Compilare: main.cpp: In function 'int main()': main.cpp:59:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for ( j = 0 ; j < columns.size () ; ++ j ) ~~^~~~~~~~~~~~~~~~~ main.cpp:64:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for ( i = 0 ; i < lines.size () ; ++ i ) ~~^~~~~~~~~~~~~~~ main.cpp:19:25: warning: unused variable 'poz' [-Wunused-variable] int n , m , i , j , poz , l , ans = NMAX * NMAX , x , y ; ^~~ main.cpp:76:26: warning: 'y' may be used uninitialized in this function [-Wmaybe-uninitialized] out << x << ' ' << y ; ^ main.cpp:76:17: warning: 'x' may be used uninitialized in this function [-Wmaybe-uninitialized] out << x << ' ' << y ; ^~~